X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 17 Aug 2007 01:07:22 -0400 Message-ID: X-Original-Return-Path: Received: from alnrmhc15.comcast.net ([204.127.225.95] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2267842 for lml@lancaironline.net; Fri, 17 Aug 2007 00:36:59 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.225.95; envelope-from=j.hafen@comcast.net Received: from hafenj1 (71-36-68-152.slkc.qwest.net[71.36.68.152]) by comcast.net (alnrmhc15) with SMTP id <20070817043620b15009d4cqe>; Fri, 17 Aug 2007 04:36:20 +0000 From: "John Hafen" X-Original-To: "'Lancair Mailing List'" Subject: I think the Farmers Daughter would like you.... X-Original-Date: Thu, 16 Aug 2007 22:36:12 -0600 X-Original-Message-ID: <000001c7e088$26101230$0a00a8c0@engagethoughtware.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7E055.DB75A230" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7E055.DB75A230 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable If you can jump from 8 feet without permanent injury, then you are = younger than I. And the farmers daughter would probably prefer you over me. =20 Vectoring your chute into the wind slows your descent. You can't do = that with a BRS. =20 John Hafen =20 -----Original Message----- From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Mark Sletten Sent: Thursday, August 16, 2007 7:19 PM To: lml@lancaironline.net Subject: [LML] Re: Apologies to the farmer's daughter =20 =20 =20 I believe the analogy describing the impact by referring to falling or jumping from a particular height doesn't account for the attitude of a BRS-equipped aircraft on impact with the ground following chute = deployment. Since the aircraft descends in a nose-low attitude, the nose hits first (assuming level ground) absorbing a great deal of the impact energy -- = the rest of the airframe would rotate downwards behind the nose until coming = to rest (upright hopefully). Assuming the main gear hits after the nose, = this would dissipate even more energy as it (the landing gear) is designed to absorb landing energies. =20 In short, landing under a BRS would be more like two smaller impacts = instead of a single large one. =20 During jump training in the USAF we learned to do the same thing with = our bodies; the Air Force calls it a Parachute Landing Fall - I don't know = what the other services call it. Essentially you land into the wind - feet = first - then roll forward while rotating your body so as to dissipate the = impact energy. Instead of keeping your feet and legs rigid so as to absorb the = full impact - as the Cirrus would if it pancaked flat onto the ground - you = roll sideways allowing your knees, hips and shoulders to take their share of = the beating. If done properly, one can easily jump from 8 feet without (permanent) injury. =20 Mark =20 _____ =20 From: rtitsworth [mailto:rtitsworth@mindspring.com]=20 Sent: Wednesday, August 15, 2007 5:47 PM To: lml@lancaironline.net Subject: RE: [LML] Apologies to the farmer's daughter =20 Rob, etal, =20 FYI: 25fps ~=3D 17 mph. About like running (full sprint) into solid = wall. Perhaps survivable, by OUCH. =20 More math. Gravitational acceleration is approx 32ft/sec^2 (drag-less freefall at = the Earth's surface) Doing some algebra to solve for the time to reach 25 fps results in: (25/32)^.5 =3D 0.88 seconds Doing some integral calculus (not shown) results in a distance traveled = of approx 7.5 feet Thus, 25 f/s is about the impact speed from falling off the top step of = an 8' step ladder Be careful when cleaning your gutters out there :-) =20 Or another analogy (in case you haven;t fallen off the top of a 8' step ladder lately), terminal velocity from the top of a 34" bar stool would = be approximately 12.5 fps (note: 1/2 speed =3D 1/4 of the impact energy). =20 Rick =20 ------=_NextPart_000_0001_01C7E055.DB75A230 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

If you can jump from 8 feet without permanent injury, then you are younger than I.  And the farmers = daughter would probably prefer you over me.

 

Vectoring your chute into the wind = slows your descent.  You can’t do that with a = BRS.

 

John Hafen

 

-----Original = Message-----
From: Lancair Mailing = List [mailto:lml@lancaironline.net] On = Behalf Of Mark Sletten
Sent: Thursday, August = 16, 2007 7:19 PM
To: = lml@lancaironline.net
Subject: [LML] Re: = Apologies to the farmer's daughter

 

 

 

I believe the analogy describing the impact = by referring to falling or jumping from a particular height doesn’t = account for the attitude of a BRS-equipped aircraft on impact with the ground = following chute deployment. Since the aircraft descends in a nose-low attitude, = the nose hits first (assuming level ground) absorbing a great deal of the impact = energy -- the rest of the airframe would rotate downwards behind the nose until = coming to rest (upright hopefully). Assuming the main gear hits after the nose, = this would dissipate even more energy as it (the landing gear) is designed to = absorb landing energies.

 

In short, landing under a BRS would be more = like two smaller impacts instead of a single large one.

 

During jump training in the USAF we learned = to do the same thing with our bodies; the Air Force calls it a Parachute Landing = Fall – I don’t know what the other services call it. Essentially = you land into the wind – feet first – then roll forward while = rotating your body so as to dissipate the impact energy. Instead of keeping your feet = and legs rigid so as to absorb the full impact – as the Cirrus would = if it pancaked flat onto the ground – you roll sideways allowing your = knees, hips and shoulders to take their share of the beating. If done properly, = one can easily jump from 8 feet without (permanent) = injury.

 

Mark

 

From: rtitsworth [mailto:rtitsworth@mindspring.com]
Sent: Wednesday, August = 15, 2007 5:47 PM
To: = lml@lancaironline.net
Subject: RE: [LML] = Apologies to the farmer's daughter

 

Rob, = etal,

 

FYI:  25fps = ~=3D 17 mph.  About like running (full sprint) into solid wall. =  Perhaps survivable, by OUCH.

 

More = math…

Gravitational acceleration is approx 32ft/sec^2 (drag-less freefall at the = Earth’s surface)

Doing some = algebra to solve for the time to reach 25 fps results in:  (25/32)^.5 =3D 0.88 = seconds

Doing some = integral calculus (not shown) results in a distance traveled of approx 7.5 = feet

Thus, 25 f/s is = about the impact speed from falling off the top step of an 8’ step = ladder

Be careful when = cleaning your gutters out there J

 

Or another = analogy (in case you haven;t fallen off the top of a 8’ step ladder lately), = terminal velocity from the top of a 34” bar stool would be approximately = 12.5 fps (note: 1/2 speed =3D 1/4 of the impact energy).

 

Rick

 

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